Method and system for the remediation of aquatic facilities

ABSTRACT

A system and method for controlling the remediation of aquatic facilities using at least one sanitizer sensor, a pH sensor, a temperature sensor and a chlorine dioxide sensor all interfaced with a programmable controller that is programmed to implement a remediation cycle and configured to calculate a Ct value, the sensors being in fluid contact with water of the aquatic facility, and the programmable controller is interfaced with a chemical feed system for supplying chlorine dioxide to the water.

FIELD OF INVENTION

The invention relates to a method and system for remediation of thewater of an aquatic facility using a programmable controller programmedto implement a remediation cycle and configured to calculate a Ct value,track the Ct value in real-time and continue the remediation cycle untila target Ct value is achieved.

BACKGROUND

Free chlorine and free bromine are common sanitizers for the treatmentof aquatic facilities. While effective at controlling bacteria counts inthe water, they have limited efficacy against waterborne pathogens thatare resistant to the sanitizers such as Cryptosporidium.

The Centers for Disease Control and Prevention has reported waterbornepathogens such as Cryptosporidium are accountable for nearly 80% of allRecreational Water Illness (RWI) in the United States. To a lesserdegree but still significant are other waterborne pathogens such asLegionella that are resistant to chlorine due to the formation ofbiofilm that protect the bacteria from the chlorine.

Chlorine dioxide is favored over many oxidizing biocides due to itsbiocide efficacy over a broad pH range, low use rate, biofilmpenetration and high selectivity in contaminated water.

In order to ensure aquatic facilities are properly protected fromwaterborne pathogens, there is a need for controlling two types ofapplications used for remediating. The first is a daily remediation andthe second is a rapid recovery shock.

Daily remediation is necessary due to the fact that aquatic facilitiesthat have been compromised by a waterborne pathogen such asCryptosporidium will not know they have been compromised until symptomsare identified and confirmed often many days or even weeks later. By thetime confirmation is made, the pathogen can spread to hundreds or eventhousands of people who used the aquatic facility and/or have spread thepathogen to other aquatic facilities thereby propagating the spread ofinfection. Implementing an automated system that remediates the aquaticfacility on a daily basis would dramatically reduce the potential forinfection as well as virtually eliminate the spread to other aquaticfacilities.

Rapid recovery shock is applied when a known event such as a fecalrelease is identified. The control system can be manually activated toimplement a remediation cycle, track the Ct value in near real-time, andterminate the remediation cycle when the targeted Ct value has beenachieved. Furthermore, the control system can then be programmed toneutralize excess treatment (e.g. chlorine dioxide and/or excesssanitizer) after achieving the target Ct value to prepare the aquaticfacility for opening to the public.

U.S. Pat. Nos. 7,922,933, 7,927,509, and 7,976,725 which are hereinincorporated by reference in their entirety, disclose a cyclic processfor the in-situ generation of chlorine dioxide. The cyclic processutilizes bromide ions that are activated by an oxidant to produce freebromine. The free bromine oxidizes chlorite ions producing chlorinedioxide. Chlorine dioxide inactivates microbiological organisms (i.e.Cryptosporidium). During this process the free bromine and at least someportion of the chlorine dioxide are reduced back to bromide ions andchlorite ions respectively which are recycled back to free bromine andchlorine dioxide utilizing the cyclic process.

U.S. application Ser. Nos. 16/501,355 and 16/501,567 which are hereinincorporated by reference in its entirety, discloses methods for in-situgeneration and stabilization of chlorine dioxide in the water of anaquatic facility using UV activation of chlorite ions.

SUMMARY OF THE INVENTION

Objectives of the invention include mitigating over 80% of allRecreational Water Illness (RWI) as described by the Centers for DiseaseControl and Prevention.

The objectives of the invention and other objectives can be obtained bya method for controlling the remediation of water of an aquaticfacility, the method comprising:

-   -   providing a system comprising at least one sanitizer sensor for        measuring a concentration of sanitizer in the water, a pH sensor        for measuring a pH of the water, a temperature sensor for        measuring a temperature of the water, and a chlorine dioxide        sensor for measuring a concentration of chlorine dioxide in the        water, the at least one sanitizer sensor, pH sensor, temperature        sensor and chlorine dioxide sensor being interfaced with a        programmable controller that is programmed to implement a        remediation cycle and configured to calculate a Ct value of the        water, and the programmable controller is interfaced with a        chemical feed system that is in fluid contact with the water;    -   measuring a temperature of the water by the water temperature        sensor;    -   implementing a remediation cycle by the programmable controller;    -   introducing chlorine dioxide into the water by the chemical feed        system;    -   measuring a chlorine dioxide concentration by the chlorine        dioxide sensor;    -   recording the chlorine dioxide concentration and calculating a        Ct value by the programmable controller;    -   sustaining the chlorine dioxide concentration until a targeted        Ct value is reached to achieve remediation;    -   measuring a pH of the water by the pH sensor;    -   adding a pH adjusting chemical to the water by the chemical feed        system;    -   measuring a concentration of sanitizer by the at least one        sanitizer sensor; and    -   adding sanitizer to the water by the chemical feed system.

The objectives can also be obtained by a system for controlling theremediation of water in an aquatic facility, the system comprising:

-   -   a programmable controller;    -   at least one sanitizer sensor in fluid communication with the        water and connected to the programmable controller;    -   a pH sensor in fluid communication with the water and connected        to the programmable controller;    -   a temperature sensor in fluid communication with the water and        connected to the programmable controller;    -   a chlorine dioxide sensor in fluid communication with the water        and connected to the programmable controller;    -   a chemical feed system in fluid contact with the water and        connected to the programmable controller, the chemical feed        system configured to supply chlorine dioxide, sanitizers, and pH        adjusting chemicals to the water; and    -   wherein the programmable controller is programmed to implement a        remediation cycle and configured to calculate a Ct value, track        the Ct value in real-time and continue the remediation cycle        until the target Ct value is achieved, and a pH and sanitizer        concentration is controlled by the programmable controller.

The programmable controller calculates, records, and stores the Ctvalue. The programmable controller can also display the Ct value. Theprogrammable controller can be programmed to forecast the time toachieve the desired Ct value. The calculated Ct value can be based onthe rolling average of the chlorine dioxide concentration. The Ct valueis calculated at any desired interval, for example every 0.1 to 60minutes. The Ct value can be calculated by:

Ct value=Σ[(X _(n) ÷n)×T]

-   -   Where:    -   “X” is the chlorine dioxide concentration in mg/l (or ppm).    -   “n” is the number of chlorine dioxide values recorded over the        sampling period.    -   “T” is the period of time (minutes) that has lapsed over the        sampling period.

Any suitable sanitizer sensor can be utilized, such as an ORP sensor oran amperometric sensor. The system preferably utilizes both ORP andamperometric sensors.

The implementation of the remediation cycle can be initiatedautomatically or manually, as desired. The programmable controller canbe programmed to terminates the remediation cycle at a desired time.

Chlorine dioxide can be introduced to the water as desired from theremediation feed system and in any way. Preferably the chlorine dioxideintroduction is a cyclic process. The remediation feed system caninclude, for example, a chlorine dioxide generator for generatingchlorine dioxide, or by UV activation of chlorite ions. Preferably,chlorine dioxide is introduced to the water using a chlorine dioxidegenerator and/or cyclic process.

The system can further comprise neutralizing excess chlorine dioxideand/or neutralizing excess sanitizer by reducing agents fed to the waterfrom a reducing agent feed system.

The programmable controller can be programmed to evaluate previousremediation cycles to determine the required application rate ofchlorine dioxide to forecast future remediation cycles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the chlorine dioxide concentration and calculated CtValue (min×mg/l) for a daily remediation (test #1) using the cyclicprocess for the in-situ generation of chlorine dioxide.

FIG. 2 illustrates the events log for test #1 using ORP as the means forcontrolling the feed of chlorine. Note with the addition of Cryptolyte®(sodium chlorite) caused the ORP to drop resulting in the feed ofchlorine. The chlorine concentration elevated as a result. As the cyclicprocess depleted the chlorite, the ORP gradually increased.

FIG. 3 illustrates the chlorine dioxide concentration and calculated CtValue (min×mg/l) for a daily remediation (test #2) using the cyclicprocess for the in-situ generation of chlorine dioxide. In this test,the chlorine concentration remained stable illustrating what occurs whenthe control system is converted to amperometric control of the chlorinefeed.

FIG. 4 illustrates the free chlorine in test #2 measured using anamperometric sensor remained relatively constant during the remediationprocess.

FIG. 5 illustrates test #3 which represented a Rapid Recovery Shockduring daytime hours. This treatment method exemplifies the methodemployed to recover an aquatic facility quickly after a known event suchas a fecal release.

FIG. 6 illustrates the events that took place during test #3.

FIG. 7 illustrates the Ct values (min×mg/l) for achieving various logreductions in viable Cryptosporidium using the cyclic process. Themethod employed represents a Rapid Recovery Shock.

FIG. 8 illustrates the Ct values (min×mg/l) for achieving various logreductions in viable Cryptosporidium using the cyclic process. Themethod employed represents a Daily Remediation.

FIG. 9 illustrates the cyclic process for the in-situ generation ofchlorine dioxide.

FIG. 10 illustrates a remediation system for remediating the water of anaquatic facility.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be explained with reference to attached non-limitingFigs. FIG. 10 illustrates an exemplary remediation system 2 forremediation of the water 4 in an aquatic facility. In an aquaticfacility, the water 4, such as in a swimming pool, typically flows outof the pool through exit conduit 32 to a surge tank 6, water pump 18,filter 20, heater 22, and then back into the pool via return conduit 33.A chemical feed system 40 is connected to the water 2, such as throughthe conduit 32. Examples of chemical feed systems 40 include a sanitizerfeed system 30 for supplying sanitizer to the water 4, a pH control feedsystem 27 for supplying chemicals to adjust or control the pH of thewater 4, a remediation feed system 26 for supplying remediationchemicals to the water 4, and a reducing agent feed system 38 forsupplying a reducing agent or other chemicals to the water 4.

A first sanitizer sensor 8 and a second sanitizer sensor 10 can be usedmeasure the concentration of sanitizer in the water 4. For example, thefirst sanitizer sensor 8 can be an ORP senor and the second sanitizersensor 10 can be amperometric type sensor. A pH sensor 12 can be used tomeasure the pH of the water 4. A chlorine dioxide sensor 14 can be usedto measure the concentration of chlorine dioxide in the water 4. Atemperature sensor 16 can be used to measure the temperature of thewater 4. A flow sensor 17 can be used to measure the water flow throughthe conduit 36 from which the sensors 8, 10, 12, 14, 16 and 17 areconnected to sample the water 4.

A programmable controller 24 is used to control the system 4. Theremediation feed system 26, the pH control feed system 28 and thesanitizer feed system 30 can be connected to and controlled by theprogrammable controller 24. The sensors 8, 10, 12, 14, 16 and 17 can beconnected to and controlled by the programmable controller 24.

The Florida Department of Health pH range for the water 4 of an aquaticfacility is from 7.2 to 7.8 with the recommended range being 7.4 to 7.6.During a remediation cycle, the programmable controller 24 automaticallymonitors and controls the pH to operate within these ranges using the pHsensor 12 and pH feed system 28. Due to the significant lag time betweenthe time of feeding pH related chemicals (i.e. acid) from the pH feedsystem 28 and the time to return a representative sample for the pHsensor 12 to measure, control logic is used to minimize the potentialfor overfeed of the chemical. One example of control logic istime-proportioned control.

The Florida Department of Health Sanitizer range for chlorine (reportedas Cl₂) sanitizer is from 1-10 ppm in pools and 2-10 ppm in spas. Forbromine (reported as Br₂) the ranges is 1.5-10 ppm in pools and 3-10 ppmin spas. During a daily remediation cycle the programmable controllerwill automatically control the feed of sanitizer within these rangesusing the first and second sanitizer sensors 8 and 10 and sanitizer feedsystem 30. However, during a rapid recovery shock, the range of chlorinewill be 1-50 ppm as Cl₂ in the case of chlorine and 2-100 ppm as Br₂.

During the remediation cycle the chlorine dioxide concentration,measured by the chlorine dioxide sensor 14, can vary based on the typeof remediation. For a daily remediation cycle, the chlorine dioxideconcentration can range from 0.0 to 2.0 ppm as ClO₂. When theremediation cycle begins, the chlorine dioxide concentration at Time=0is 0.0 ppm. Over time the concentration of chlorine dioxide willincrease. The desired maximum concentration is dependent on the timeconstraints to achieve the desired Ct value. When longer times arepermitted such as in the case of an evening remediation when the aquaticfacility is closed to the public, the maximum concentration of chlorinedioxide maybe as low as 0.1 ppm as ClO₂. In the event of a rapidrecovery shock, it may be more desirable to increase to maximumconcentration in the water as high as 20 ppm as ClO₂ to minimize thetime the aquatic facility is closed to the public. Regardless of therange or maximum concentration of chlorine dioxide achieved, as long asthe desired Ct value is achieved then remediation has been achieved.

The Ct value (min×mg/l) can range from 1-200, more preferred 2-180, andmost preferred 5-160. The optimum Ct value will depend on what is beingremediated and the method of remediation being used. Referring to FIGS.7 and 8, the charts illustrate the log reduction for Cryptosporidium forvarious Ct values using the cyclic process. Depending on the method usedthe Ct value required to remediate the Cryptosporidium (3-log reduction)varied. In the case of penetrating and removing biofilm in the piping ofan aquatic facility the Ct value may be higher depending on thethickness and surface area covered by the biofilm.

The programmable controller 24 tracks the chlorine dioxide concentrationmeasured by the chlorine dioxide sensor 14 during the remediation cycleand calculates the rolling average (also referred to as a “movingaverage”). The rolling average is multiplied by the time that has lapsedmeasured in minutes to update the Ct value in real-time. The rollingaverage can be updated over any desired period of lapsed time. Onepreferred period of lapsed time ranges from 0.1 to 60 minutes, morepreferred 0.2 to 30 minutes, and most preferred 0.5 to 10 minutes. Theability to frequently update the real-time Ct value allows theprogrammable controller to forecast the trend and project when thetargeted Ct value will be reached.

The ability to forecast when a remediation will be achieved, theprogrammable controller 24 can be programmed to learn from the previousremediation cycles and project and/or automatically adjust theconcentration of chlorine dioxide and/or the application rate ofchlorine dioxide in future remediation cycles to achieve a targeted Ctvalue within a desired time interval. For example, when usingtime-proportioned control logic, the controller 24 alters the feedduration of chlorine dioxide from the remediation feed system 26 basedon how far the measured concentration of chlorine dioxide measured bythe sensor 14 is from the set-point. If the sun's UV for exampledecomposes the chlorine dioxide at a high rate, the time required toachieve Ct value can be substantially increased. By evaluating thenumber of feed cycles, duration of the feed cycles, and the deviationsfrom the set-point during and after said feed cycles, corrections can bemade to compensate for the losses in chlorine dioxide concentration aswell as the lag-times between applying chlorine dioxide and observing(measuring) the result.

The remediation cycle may comprise a single application of chlorinedioxide. For example, referring to FIGS. 1 and 2 illustrate that asingle application of sodium chlorite under the brand name Cryptolyte®provided sufficient chlorine dioxide using the cyclic process to achievea 3-log reduction in Cryptosporidium in only 7 hours. The remediationcycle began with the feed of Cryptolyte® at 8:00 pm and by 3:00 am theremediation cycle had achieved a Ct value of 66 (min×mg/l). Referring toFIG. 8, a Ct value of 66 (min×mg/l) is sufficient to remediateCryptosporidium.

The remediation cycle may also apply multiple applications of chlorinedioxide. For example, when the remediation cycle uses ex-situ generationof chlorine dioxide such as in the case of using a chlorine dioxidegenerator as part of the remediation feed system 26, the programmablecontroller 24 can control the concentration of chlorine dioxide byapplying multiple applications of chlorine dioxide to sustain apredetermined set-point of chlorine dioxide.

The remediation cycle can be automatically initiated by the programmablecontroller 24 such as in the case of planned evening remediation whenthe aquatic facility is closed to the public. However, fin the case of afecal release, the remediation cycles can be initiated manually, thencarry out the functions automatically to perform the remediation.

The programmable controller 24 can be configured to calculate, record,and store the Ct value. Optionally the controller 24 can display the Ctvalue on the display 25 and callout to a technician in the event of asuccessful or failed remediation cycle. Once the Ct value has beenachieved, the controller 24 terminates the remediation cycle.

What a targeted Ct value is achieved and the remediation cycle isterminated, adjustments to the water 4 chemistry may be required beforeopening the aquatic facility to patrons. In some cases such as a rapidrecovery shock, excess sanitizer and chlorine dioxide can make the waterunsuitable to swimmers. Neutralizing the excess sanitizer and chlorinedioxide can be automated by the system. The amperometric sensor 10measures the excess chlorine as well as chlorine dioxide. The chlorinedioxide sensor 14 measures specifically chlorine dioxide. The differencebetween the two sensors 10 and 14 provides a relative concentration ofsanitizer.

A reducing feed system 38 interfaced with the programmable controller 24and in fluid contact with the water 4 of the aquatic facility providesthe ability to feed a reducing agent exemplified by sodium thiosulfatein order to neutralize the excess oxidizers (sanitizer etc.), or anyother desired chemicals. Furthermore, knowing the strength of the sodiumthiosulfate solution, the feed rate of the chemical feed system 40, thevolume of water to be treated etc., the programmable controller 24 canbe programmed to calculate how much reducing agent to apply, then trackthe reductions in excess and adjust as needed until the water meets thewater chemistry requirements to open.

The following terms used throughout the specification have the followingmeanings unless otherwise indicated.

“A” or “an” means “at least one” or “one or more” unless otherwiseindicated.

“Comprise”, “have”, “include” and “contain” (and their variants) areopen-ended linking verbs and allow the addition of other elements whenused in a claim. “Consisting of” is closed, and excludes all additionalelements.

“Consisting essentially of” excludes additional material elements, butallows the inclusions of non-material elements that do not substantiallychange the nature of the invention.

“Effective amount” refers to an amount of metal-porphyrin catalystsufficient to impart a measurable reduction in the concentration ofhalogenated decomposition byproducts (DBPs) and/or organic contaminants(all comprising “oxidant demand”) that form decomposition byproducts(precursors) compared to results achieved by applying persulfate donorwithout an effective amount of said catalyst.

As used herein, the term “aquatic facility” is used with reference toall structural components and equipment comprising an aqueous systemused by humans for exercise, sports and/or recreation. Examples ofaquatic facilities include but are not limited to: residential swimmingpools, water parks, theme parks, swimming pools, spas, therapy pools,hot tubs and the like.

As used herein, the term “aqueous system” describes a body of water 4that can be treated using the disclosed composition. Examples of aqueoussystems include recreational water, cooling towers, cooling ponds andwastewater.

As used herein, “recreational water” is water 4 used by mammals (i.e.humans) for various activities such as swimming, exercise, water sports,recreation, physical therapy and diving. Examples of aqueous systemscomprising recreational water include: swimming pools, hot tubs, featurepools, spas, water-park rides, therapy pools, diving wells etc.

As used herein the term “Ct value” is defined as a value having theunits (mg/l×min). One means for determining the Ct value is exemplifiedby calculating the product of the average concentration of an oxidant(mg/l) and time (minutes) of exposure to the oxidant. For example, ifthe average chlorine dioxide concentration of ClO₂ is determined to be2.2 mg/l over a 20 minute period of time, the Ct value is calculated bymultiplying the average concentration of chlorine dioxide by the time.

Ct value=2.2 mg/l×20 min

Ct value=44(min×mg/l)

Another example is exemplified by calculating the sum of theconcentration times time over incremental periods. For example, thegeneral equation:

Ct value=Σ[X _(n) ÷n)×T]

Illustrates that the sum of the average concentration measured over anincrement of time provides an effective means of determining the Ctvalue. This method of determining the Ct value allows for anaccumulating Ct value over short increments of time rather than longerperiods as illustrated above.

The Ct value can be targeted based on laboratory and/or field studies toachieve the desired level of inactivation. Comparatively, low Ct values(i.e. Ct=1 mg·min/l) may achieve a 6-log reduction in bacteria like E.coli, while higher Ct values (i.e. Ct=90 mg·min/l) may be required toreduce a parasite like Cryptosporidium by 3-log.

As used herein, “algorithm to calculate the Ct value” describes amathematical equation for calculating the Ct value in near real-time.One example of a suitable algorithm for calculating the Ct valuefollows:

Ct value=(X _(n) ÷n)×T

-   -   Where:    -   “X” is the chlorine dioxide concentration in mg/l (or ppm).    -   “n” is the number of chlorine dioxide values recorded over a        period of time since beginning the remediation cycle.    -   “T” is the period of time (minutes) that has lapsed since        beginning the remediation cycle.

Another example of a suitable algorithm for calculating the Ct valuefollows the general equation:

Ct value=Σ[(X _(n) ÷n)×T]

-   -   Where:    -   “X” is the chlorine dioxide concentration in mg/l (or ppm).    -   “n” is the number of chlorine dioxide values recorded over the        sampling period of time.    -   “T” is the period of time (minutes) that has lapsed during the        sampling period.

The algorithm calculates the Ct value over the period of the remediationcycle. The algorithm calculates the sum of all the chlorine dioxidevalues recorded. The sum is divided by the number of chlorine dioxidevalues to obtain the average chlorine dioxide concentration. The averagechlorine dioxide concentration is then multiplied by the lapsed time(minutes) to calculate the Ct value (mg/l×min). The Ct value is updatedin real-time by calculating the rolling average of the chlorine dioxideconcentration, then multiplying the rolling average by the lapsed time(minutes) since beginning the remediation cycle.

As used herein, “rolling average” is the average chlorine dioxideconcentration resulting from the accumulated chlorine dioxideconcentrations (mg/l) divided by the number of chlorine dioxidemeasurements by the chlorine dioxide sensor 14 and recorded. The rollingaverage is used to provide a real-time Ct value by multiplying therolling average by the remediation cycle's lapsed time (i.e. number ofminutes since beginning the remediation cycle), or the lapsed timeduring the sampling period. The rolling average can be updated over anydesired period of lapsed time. One preferred period of lapsed timeranges from 0.1 to 60 minutes, more preferred 0.2 to 30 minutes, andmost preferred 0.5 to 10 minutes.

As used herein, the term “remediation cycle” describes the process ofintroducing chlorine dioxide into the water of an aquatic facility at aconcentration sufficient to achieve a targeted Ct value (min×mg/l). Thechlorine dioxide can be introduced to the water 4 from the remediationfeed system 26 using ex-situ and/or in-situ methods. An ex-situ methodmay comprise an chlorine dioxide generator as part of the remediationfeed system 26. An in-situ method may comprise the cyclic process and/orUV activation of chlorite as part of the remediation feed system 26. Theex-situ method can be coupled with the in-situ method to accelerate theconcentration of chlorine dioxide using a chlorine dioxide generator aswell as maximize efficiency using the cyclic process.

As used herein, the term “cyclic process” relates to the recycling ofsubstantially inert anions comprising bromide and chlorite into theiroxyhalogen surrogates, exemplified by hypobromous acid and chlorinedioxide respectfully followed by reduction back to their respectiveanions, and where the process is repeated (FIG. 9). The cyclic processcomprises activating bromide ions with an oxidant to produce freebromine, the free bromine oxidizes chlorite ions to produce chlorinedioxide, and reducing at least some free bromine back to bromide ions.

As used herein, the term “chlorite anion donor” and “chlorite donor” isa compound that comprises an alkali metal salt comprising chloriteanions ClO₂ ⁻, chlorine dioxide, or any convenient direct or indirectsource of chlorite anions. For example, chlorine dioxide can indirectlyproduce chlorite due to reduction in an aqueous system. Sodium chloritedirectly supplies chlorite anions.

As used herein, the term “chlorite anion” (also referred to as“chlorite”) comprises chlorite having the general formula ClO₂ ⁻. Thechlorite is the anion released when sodium chlorite is dissolved inwater and converts to chlorine dioxide.

As used herein, the term “recycled” means at least some portion of therecovered bromide anions and chlorite anions are regenerated to theirrespective oxyhalogen compounds, followed by reduction back to theirrespective anions, and where the process is repeated.

As used herein, the term “Cryptosporidium” is used to represent any formof parasitic microbiological organism from the family ofCryptosporidium. An example of Cryptosporidium is Cryptosporidium parvum(also referred to as C. parvum, C. parvum and Cryptosporidium parvum).Other examples of Cryptosporidium include but are not limited to: C.hominis, C. canis, C. felis, C. meleagridis, and C. muris. It is to benoted that inclusion or exclusion of italic characters or print whenreferring to Cryptosporidium or any of its many variants does not in anyway detract from its intended descriptive meaning.

As used herein, the term “microbiological organisms” is used withreference to all forms of microbiological life including: parasites,bacteria, viruses, algae, fungus, and organisms encased in biofilms.

As used herein, “parasites” includes any species of organism includingCryptosporidium, Giardia and Ameba that can be transferred to humans bywater and cause waterborne parasitic disease in humans.

As used herein, the term “inactivation” is used with reference to theability to deactivate, kill, or destroy microbiological organisms.

As used herein, “remediation” is defined as the ability to reduce thelevel of waterborne pathogens and/or algae to levels at or below thatdeemed acceptable by various regulatory agencies exemplified by Stateand local Departments of Health, U.S. Environmental Protection Agency,and/or the Centers for Disease Control and Prevention. Examples ofachieving remediation comprise at least one of the following: less than1 CFU per ml of viable bacteria determined by heterotrophic plate count;greater than or equal to a 3-log reduction of parasites, and/orrendering the aqueous system free of algae.

As used herein, “remediation” is used with reference to achieving the Ctvalue necessary to achieve at least a 6-log reduction in gram negativeand/or gram positive bacteria, virus &/or at least a 3-log reduction ofparasites. Remediation is also used in reference to the ability torender the aqueous system free of algae.

As used herein, “programmable controller” 24 describes a control systemcomprising at least a microprocessor and/or programmable logiccontrollers (PLC) with relays and interfaces with sensors and chemicalfeed systems. The operations described herein can be implemented asexecutable code stored on a computer or machine readable non-transitorytangible storage medium in communication with the microprocessor.

Non-limiting examples of how the programmable controller 24 can be usedto control chemical feed systems 40 includes: actuating chemical feed;varying the rate of chemical feed; energizing an electronic device suchas a chemical feed pump, solenoid valve; stopping chemical feed; andinitiating a neutralization cycle that removes residual chemicals fromthe water using neutralizing chemicals exemplified by sodium sulfite.The programmable controller 24 receives inputs either manually and/orautomatically from sensors exemplified by the non-limiting examples: pHsensor 12, ORP sensor 8, amperometric sensor 10, chlorine dioxide sensor14, temperature sensor 16, flow sensor 17, flow switch and the like.

The programmable controller 24 uses some form of control logic tocontrol and optimize the feed of chemicals. Examples of control logicinclude: time-proportional, proportional, derivative, integral,proportional-integral-derivative control.

As used herein, “fluid contact” describes contact between conduits 32,33 capable of transporting liquid to and from the main body of water(i.e. swimming pool) 4 at the aquatic facility. Specifically regardingaquatic facilities, sensors and chemical feed systems 40 are in fluidcontact with the water 4 of an aquatic facility in or near themechanical room where water is recovered from the pool, filtered 20,sometime heated 22 and returned to the pool. The piping (conduit) 36transporting the water supplies water for the sensors to monitor thevarious parameters such as pH 12, sanitizer concentration 8, 10,temperature 16 and chlorine dioxide 14. Chemical feed 40 is generallyapplied into the return piping 33 after being filtered and whereapplicable heated to prevent corrosion of the heater 22.

As used herein, “chemical feed systems” 40 describe any convenientdevice that is fluid contact with both the chemicals and the water ofthe aquatic facility. The chemical feed systems 40 can be controlled todeliver the desired amount of chemicals exemplified by the non-limitingexamples chlorine, acid such as HCl or CO₂ and sodium chlorite.Non-limiting examples of chemical feed systems include: chemicalmetering pumps, educators, modulating control valves and the like.

As used herein, “flow sensor” 17 describes a device that can detect aliquid flowing through a pipe or conduit 36. The flow sensor 17 can be aflow transmitter that measures the flow rate, but is not required tomeasure the flow rate. The flow sensor 17 detects motive water in thepipe or conduit 36. One non-limiting example of a flow sensor that doesnot measure the flow rate is a Rotorflow® Flow Sensor available by Gems™Sensors and Controls.

As used herein, “energize” and “energizing” and its variations describesthe activation of an electrical device by closing a circuit thatdelivers an electrical current to the electrical device so that theelectrical device performs a desired function. For example, a flowsensor detects motive water followed by the control panel energizing thechemical feed systems. In contrast, when motive water is no longerconfirmed by the flow sensor, the control panel stops the chemical feedsystems.

As used herein, “actuated” and “actuating” and its variations is anaction initiated by the control panel to cause something to happen suchas initiating chemical feed, stopping chemical feed, initiating aneutralization cycle and the like.

As used herein, the term “free chlorine” is used with reference to achlorine source that hydrolyses in the aqueous system to produce atleast some portion of hypochlorous acid and hypochlorite ions.

As used herein, the term “free bromine” is used with reference to theformation or presence of hypobromous acid and possibly some portion ofhypobromite ions.

As used herein, the term “inactivation” is used with reference to theability to deactivate, kill, or destroy microbiological organisms.

As used herein, the term “microbiological organisms” is used withreference to all forms of microbiological life forms including:parasites, bacteria, viruses, algae, fungus, and organisms encased inbiofilms.

As used herein, the term “free halogen donor” is used with reference toa halogen source which acts as an active oxidizer when dissolved inwater. Chlorine based free halogen donors form at least one of Cl₂,HOCl, and OCl⁻ (also referred to as free chlorine) when added to water,whereby the species formed is pH dependent. Bromine based free halogendonors form at least one of Br₂, HOBr, and OBr⁻ (also referred to asfree bromine), again the species being pH dependent.

As used herein, “sensor for controlling the feed of sanitizer” is usedwith reference to ORP and/or amperometric sensors that are in fluidcontact with the water of an aquatic facility, and provide measurementsused for controlling the feed of a sanitizer (e.g. chlorine and/orbromine). While only one sensor is used to control the sanitizer at anygiven time, it is beneficial to monitor both ORP and free chlorine. Alsoit may be advantageous to be able to switch between sensors depending onthe method of remediation being employed. For example, daily remediationmay best be controlled using an amperometric sensor for controlling thesanitizer to limit the concentration of sanitizer in the water. Thisensures the pool can be readily opened without the need for removingexcess sanitizer before opening. However, during a rapid recovery shock,it may be advantageous to increase the sanitizer concentration toaccelerate the cyclic process when in-situ generation of chlorinedioxide is used. The ability to program the programmable controller toswitch between sensors based on the method being used can be verybeneficial.

As used herein, “amperometric sensor” 10 describes a device that is influid contact with the water of an aquatic facility and is used tomeasure the concentration of sanitizer exemplified by free chlorine. Theamperometric sensor 10 can be used to control the feed of sanitizer.

As used herein, “chlorine dioxide sensor” 14 describes a device that isin fluid contact with the water 4 of an aquatic facility and is used tomeasure the chlorine dioxide concentrated used to remediate the aquaticfacility. Generally the chlorine dioxide sensor 14 is an amperometricsensor that incorporates a gas permeable membrane that allows chlorinedioxide gas to permeate the membrane while isolating the sensor fromwater soluble oxidizers like chlorine. The chlorine dioxide sensor 14can be any suitable sensor that can be used to selectively measure thechlorine dioxide. One example of another type of chlorine dioxide sensoris a colorimetric device that utilizes lissamine green reagents toselectively measure chlorine dioxide in the presence of sanitizers.

As used herein, “ORP sensor” 8 describes a device that is in fluidcontact with the water of an aquatic facility and is used to measure theOxidation Reduction Potential (ORP) of the water 4. ORP sensor 8 can besued to control the feed of sanitizer.

As used herein, “chemical feed systems” 40 describes in broad terms anydesirable means for applying chemicals to the water 4 of an aquaticfacility. Non-limiting examples of chemical feed systems include:chemical metering pumps, educators, erosion feeders such as achlorinator or brominator.

As used herein, “Heterotrophic plate count (HPC) is also known by anumber of other names, including standard plate count, total platecount, total viable count or aerobic quality count. It does notdifferentiate between the types of bacteria present nor does it indicatethe total number of bacteria present in the water—only those capable offorming visible colonies under specified conditions on certainnon-selective microbiological media. Varying the incubation temperaturewill favour the growth of different groups of bacteria. As it gives moremeaningful information about pathogenic (disease-causing) bacteria, 35°C. (or 37° C.) is the preferred incubation temperature. HPC does notnecessarily indicate microbiological safety as the bacteria isolated maynot have been faecally-derived but it does give a measure of the overallgeneral quality of the pool water, and whether the filtration anddisinfection systems are operating satisfactorily. Results reported bythe laboratory are traditionally expressed as colony forming units permillilitre (CFU/mL) which equates to the number of bacteria in eachmillilitre of the original sample of water. A HPC count of less than 1CFU/mL indicates that the disinfection system is effective. If the countis between 10 and 100 CFU/mL, a routine investigation should beconducted as soon as possible to ensure that all the managementoperations are functioning properly.

As used herein, “CFU” (Colony Forming Units) is a unit used inmicrobiology to estimate the number of viable bacteria or fungal cellsin a sample.

EXAMPLES

A 46,000 gallon swimming pool in Boca Rotan Fla. was used as a test sitefor testing automated control of remediation cycles. Daily remediationusing the cyclic process was performed in the evening hours, while RapidRecovery Shock using both the cyclic process and UV activation ofchlorite ions was performed during daylight hours.

The swimming pool was equipped with a System 5 controller acquired fromBECS Technology,

Inc. located in Saint Louis, Mo. The System 5 controller comprised ORP,pH, amperometric and temperature sensors. A CRONOS chlorine dioxidecontroller was acquired from Process Instruments located in Lancashire,UK. The CRONOS controller was fitted with a DioSense sensor comprisingan amperometric sensor capped with a gas permeable membrane. The CRONOSwas calibrated using a lissamine green test that is specific to chlorinedioxide. Both control systems have data logging and the System 5controller further comprised events logging capability to record timeand duration of chemical feed etc.

A side stream of water circulated through the filter system was used assource of water for the described sensors. After passing thru thesensor's flow cells, the water was discharged into the diatomaceousearth filter pit.

Calcium hypochlorite was the sanitizer and hydrochloric acid was usedfor pH control. Cryptolyte® is a trademarked source of 25% active sodiumchlorite solution. The pool water was treated with granular sodiumbromide to provide approximately 15 ppm bromide ions (Br⁻).

Test #1 is represented by FIGS. 1 and 2. Test #1 consisted of a dailyremediation using the cyclic process. The sanitizer feed was controlledby ORP. The remediation cycle was initiated automatically at 8:00 pm bythe System 5 controller. Cryptolyte® was applied at a dosage of 0.2 lbsper 10,000 gallons of pool water (approximately 0.44 ppm as ClO₂ ⁻).FIG. 1 shows the chlorine dioxide concentration measured by the CRONOScontroller. The corresponding Ct values are indicated. FIG. 2illustrates the events log for Test #1. The events log shows Crytpolytewas applied beginning at 8:00 pm and the event lasted for 15 minutes.The ORP dropped significantly due to the application of sodium chloritewhich is a source of demand. The drop in ORP caused the System 5controller to begin feeding sanitizer to regain the ORP set-point. A Ctvalue of 66 (min×mg/l) was achieved in 5 hours which based on GLP dataillustrated in FIG. 8 is sufficient to achieve a 3-log reduction inCryptosporidium.

Test #2 is represented by FIGS. 3 and 4. The process of Test #1 wasrepeated with the exception the calcium hypochlorite feeder was bypassedto prevent the spike in chlorine concentration thereby representingamperometric control of the sanitizer. While the amperometricmeasurement showed virtually no change in free chlorine, the cyclicprocess allowed for the remediation cycle to achieve a Ct value of 76(min×mg/l) by 3:00 am.

Test #3 represented by FIGS. 5 and 6 illustrates a rapid recovery shockusing a combination of the cyclic process and UV activation of chloriteions. The pool water was treated with 0.5 ppm of a chromophorecomprising Keyfluor™ White CBS-X which possesses a UV absorbance peaknear 360 nm but only minimal UV absorbance at 260 nm. This allows the UVfrom the sun to activate chlorite at 260 nm but block the decompositionof chlorine dioxide with a UV peak at 360 nm. The remediation cycle wasinitiated at 9:15 am (FIG. 6). Cryptolyte was applied at a dose of 0.4lbs per 10,000 gallons of pool water providing approximately 0.88 ppm asClO₂ ⁻.

FIG. 5 illustrates a Ct value of 64 (min×mg/l) was achieve at 11:20 amjust over 2 hours and five minutes after initiation of the remediationcycle.

It is to be understood that the foregoing illustrative embodiments havebeen provided merely for the purpose of explanation and are in no way tobe construed as limiting of the invention. Words used herein are wordsof description and illustration, rather than words of limitation. Inaddition, the advantages and objectives described herein may not berealized by each and every embodiment practicing the present invention.Further, although the invention has been described herein with referenceto particular structure, steps and/or embodiments, the invention is notintended to be limited to the particulars disclosed herein. Rather, theinvention extends to all functionally equivalent structures, processesand uses, such as are within the scope of the appended claims. Thoseskilled in the art, having the benefit of the teachings of thisspecification, may affect numerous modifications thereto and changes maybe made without departing from the scope and spirit of the invention.

1. A method for controlling the remediation of water of an aquaticfacility, the method comprising: providing a system comprising at leastone sanitizer sensor for measuring a concentration of sanitizer in thewater, a pH sensor for measuring a pH of the water, a temperature sensorfor measuring a temperature of the water, and a chlorine dioxide sensorfor measuring a concentration of chlorine dioxide in the water, the atleast one sanitizer sensor, pH sensor, temperature sensor and chlorinedioxide sensor being interfaced with a programmable controller that isprogrammed to implement a remediation cycle and configured to calculatea Ct value of the water, and the programmable controller is interfacedwith a chemical feed system that is in fluid contact with the water;implementing a remediation cycle by the programmable controller;introducing chlorine dioxide into the water by the chemical feed system;measuring a chlorine dioxide concentration by the chlorine dioxidesensor; recording the chlorine dioxide concentration and calculating aCt value by the programmable controller; sustaining the chlorine dioxideconcentration until a targeted Ct value is reached to achieveremediation; and controlling a pH and sanitizer concentration by theprogrammable controller.
 2. The method according to claim 1, wherein theprogrammable computer uses an algorithm to calculate the Ct valuecomprising:Ct value=(X _(n) ÷n)×T Where: “X” is the chlorine dioxide concentrationin mg/l (or ppm). “n” is the number of chlorine dioxide values recordedover a period of time since beginning the remediation cycle. “T” is theperiod of time (minutes) that has lapsed since beginning the remediationcycle.
 3. The method according to claim 1, wherein the programmablecomputer uses an algorithm to calculate the Ct value comprising:Ct value=Σ[(X _(n) ÷n)×T] Where: “X” is the chlorine dioxideconcentration in mg/l (or ppm). “n” is the number of chlorine dioxidevalues recorded over the sampling period of time. “T” is the period oftime (minutes) that has lapsed during the sampling period.
 4. The methodaccording to claim 1, comprising calculating the Ct value based on arolling average of the chlorine dioxide concentration.
 5. The methodaccording to claim 1, wherein the at least one sanitizer sensor is anORP sensor.
 6. The method according to claim 1, wherein the at least onesanitizer sensor is an amperometric sensor.
 7. The method according toclaim 1, wherein the at least one sanitizer sensor is both ORP andamperometric sensors.
 8. The method according to claim 1, whereinimplementation of the remediation cycle is initiated automatically. 9.The method according to claim 1, wherein the implementation of theremediation cycle is initiated manually.
 10. The method according toclaim 1, wherein the programmable controller calculates, records, andstores the Ct value.
 11. The method according to claim 1, wherein theprogrammable controller displays the Ct value.
 12. The method accordingto claim 1, wherein the programmable controller terminates theremediation cycle.
 13. The method according to claim 1, wherein chlorinedioxide is introduced using the cyclic process, the cyclic processcomprising: activating bromide ions with an oxidant to produce freebromine, the free bromine oxidizes chlorite ions to produce chlorinedioxide, and reducing at least some free bromine back to bromide ions.14. The method according to claim 1, wherein chlorine dioxide isintroduced using a chlorine dioxide generator.
 15. The method accordingto claim 1, wherein the chlorine dioxide is introduced using UVactivation of chlorite ions.
 16. The method according to claim 1,wherein the chlorine dioxide is introduced using both a chlorine dioxidegenerator and cyclic process, the cyclic process comprising: activatingbromide ions with an oxidant to produce free bromine, the free bromineoxidizes chlorite ions to produce chlorine dioxide, and reducing atleast some free bromine back to bromide ions.
 17. The method accordingto claim 1, further comprising neutralizing excess chlorine dioxide. 18.The method according to claim 1, further comprising neutralizing excesssanitizer.
 19. A system for controlling the remediation of water in anaquatic facility, the system comprising: a programmable controller; atleast one sanitizer sensor in fluid communication with the water andconnected to the programmable controller; a pH sensor in fluidcommunication with the water and connected to the programmablecontroller; a temperature sensor in fluid communication with the waterand connected to the programmable controller; a chlorine dioxide sensorin fluid communication with the water and connected to the programmablecontroller; a chemical feed system in fluid contact with the water andconnected to the programmable controller, the chemical feed systemconfigured to supply chlorine dioxide, sanitizers, and pH adjustingchemicals to the water; and wherein the programmable controller isprogrammed to implement a remediation cycle and configured to calculatea Ct value, track the Ct value in real-time and continue the remediationcycle until the target Ct value is achieved, and a pH and sanitizerconcentration is controlled by the programmable controller.
 20. Theprogrammable controller according to claim 19, wherein an algorithm tocalculate the Ct value comprises:Ct value=(X _(n) ÷n)×T Where: “X” is the chlorine dioxide concentrationin mg/l (or ppm). “n” is the number of chlorine dioxide values recordedover a period of time since beginning the remediation cycle. “T” is theperiod of time (minutes) that has lapsed since beginning the remediationcycle.
 21. The programmable controller according to claim 19, whereinthe Ct value is calculated using a rolling average of chlorine dioxideconcentrations.
 22. The programmable controller according to claim 21,wherein the Ct value is calculated every 0.1 to 60 minutes.
 23. Theprogrammable controller according to claim 19, further comprising aprogram to evaluate previous remediation cycles and project theconcentration of chlorine dioxide and/or the application rate ofchlorine dioxide in future remediation cycles to achieve a targeted Ctvalue within a desired time interval.
 24. The programmable controlleraccording to claim 19, wherein an algorithm to calculate the Ct valuecomprises:Ct value=Σ[(X _(n) ÷n)×T] Where: “X” is the chlorine dioxideconcentration in mg/l (or ppm). “n” is the number of chlorine dioxidevalues recorded over the sampling period of time. “T” is the period oftime (minutes) that has lapsed during the sampling period.
 25. Theprogrammable controller according to claim 19, wherein the Ct value iscalculated using a rolling average of chlorine dioxide concentrations.26. The programmable controller according to claim 21, wherein the Ctvalue is calculated every 0.1 to 60 minutes.
 27. The programmablecontroller according to claim 19, further comprising a program toevaluate previous remediation cycles and project the concentration ofchlorine dioxide and/or the application rate of chlorine dioxide infuture remediation cycles to achieve a targeted Ct value within adesired time interval.
 28. A method for controlling the remediation ofwater of an aquatic facility, the method comprising: implementing aremediation cycle by a programmable controller; introducing chlorinedioxide into the water by a chemical feed system in communication withthe programmable controller; measuring a chlorine dioxide concentrationby a chlorine dioxide sensor in communication with the programmablecontroller; recording the chlorine dioxide concentration and calculatinga Ct value by the programmable controller; and sustaining the chlorinedioxide concentration until a targeted Ct value is reached to achieveremediation.
 29. A system for controlling the remediation of water in anaquatic facility, the system comprising: a programmable controller; achlorine dioxide sensor in fluid communication with the water andconnected to the programmable controller; a chemical feed system influid contact with the water and connected to the programmablecontroller, the chemical feed system configured to supply chlorinedioxide to the water; and wherein the programmable controller isprogrammed to implement a remediation cycle and configured to calculatea Ct value, track the Ct value in real-time and continue the remediationcycle until a target Ct value is achieved.